1 // layout.cc -- lay out output file sections for gold
3 // Copyright 2006, 2007 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
30 #include "parameters.h"
40 // Layout_task_runner methods.
42 // Lay out the sections. This is called after all the input objects
46 Layout_task_runner::run(Workqueue
* workqueue
)
48 off_t file_size
= this->layout_
->finalize(this->input_objects_
,
51 // Now we know the final size of the output file and we know where
52 // each piece of information goes.
53 Output_file
* of
= new Output_file(this->options_
,
54 this->input_objects_
->target());
57 // Queue up the final set of tasks.
58 gold::queue_final_tasks(this->options_
, this->input_objects_
,
59 this->symtab_
, this->layout_
, workqueue
, of
);
64 Layout::Layout(const General_options
& options
)
65 : options_(options
), namepool_(), sympool_(), dynpool_(), signatures_(),
66 section_name_map_(), segment_list_(), section_list_(),
67 unattached_section_list_(), special_output_list_(),
68 section_headers_(NULL
), tls_segment_(NULL
), symtab_section_(NULL
),
69 dynsym_section_(NULL
), dynamic_section_(NULL
), dynamic_data_(NULL
),
70 eh_frame_section_(NULL
), output_file_size_(-1),
71 input_requires_executable_stack_(false),
72 input_with_gnu_stack_note_(false),
73 input_without_gnu_stack_note_(false)
75 // Make space for more than enough segments for a typical file.
76 // This is just for efficiency--it's OK if we wind up needing more.
77 this->segment_list_
.reserve(12);
79 // We expect two unattached Output_data objects: the file header and
80 // the segment headers.
81 this->special_output_list_
.reserve(2);
84 // Hash a key we use to look up an output section mapping.
87 Layout::Hash_key::operator()(const Layout::Key
& k
) const
89 return k
.first
+ k
.second
.first
+ k
.second
.second
;
92 // Return whether PREFIX is a prefix of STR.
95 is_prefix_of(const char* prefix
, const char* str
)
97 return strncmp(prefix
, str
, strlen(prefix
)) == 0;
100 // Returns whether the given section is in the list of
101 // debug-sections-used-by-some-version-of-gdb. Currently,
102 // we've checked versions of gdb up to and including 6.7.1.
104 static const char* gdb_sections
[] =
106 // ".debug_aranges", // not used by gdb as of 6.7.1
112 // ".debug_pubnames", // not used by gdb as of 6.7.1
118 is_gdb_debug_section(const char* str
)
120 // We can do this faster: binary search or a hashtable. But why bother?
121 for (size_t i
= 0; i
< sizeof(gdb_sections
)/sizeof(*gdb_sections
); ++i
)
122 if (strcmp(str
, gdb_sections
[i
]) == 0)
127 // Whether to include this section in the link.
129 template<int size
, bool big_endian
>
131 Layout::include_section(Sized_relobj
<size
, big_endian
>*, const char* name
,
132 const elfcpp::Shdr
<size
, big_endian
>& shdr
)
134 // Some section types are never linked. Some are only linked when
135 // doing a relocateable link.
136 switch (shdr
.get_sh_type())
138 case elfcpp::SHT_NULL
:
139 case elfcpp::SHT_SYMTAB
:
140 case elfcpp::SHT_DYNSYM
:
141 case elfcpp::SHT_STRTAB
:
142 case elfcpp::SHT_HASH
:
143 case elfcpp::SHT_DYNAMIC
:
144 case elfcpp::SHT_SYMTAB_SHNDX
:
147 case elfcpp::SHT_RELA
:
148 case elfcpp::SHT_REL
:
149 case elfcpp::SHT_GROUP
:
150 return parameters
->output_is_object();
152 case elfcpp::SHT_PROGBITS
:
153 if (parameters
->strip_debug()
154 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
156 // Debugging sections can only be recognized by name.
157 if (is_prefix_of(".debug", name
)
158 || is_prefix_of(".gnu.linkonce.wi.", name
)
159 || is_prefix_of(".line", name
)
160 || is_prefix_of(".stab", name
))
163 if (parameters
->strip_debug_gdb()
164 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
166 // Debugging sections can only be recognized by name.
167 if (is_prefix_of(".debug", name
)
168 && !is_gdb_debug_section(name
))
178 // Return an output section named NAME, or NULL if there is none.
181 Layout::find_output_section(const char* name
) const
183 for (Section_name_map::const_iterator p
= this->section_name_map_
.begin();
184 p
!= this->section_name_map_
.end();
186 if (strcmp(p
->second
->name(), name
) == 0)
191 // Return an output segment of type TYPE, with segment flags SET set
192 // and segment flags CLEAR clear. Return NULL if there is none.
195 Layout::find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
196 elfcpp::Elf_Word clear
) const
198 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
199 p
!= this->segment_list_
.end();
201 if (static_cast<elfcpp::PT
>((*p
)->type()) == type
202 && ((*p
)->flags() & set
) == set
203 && ((*p
)->flags() & clear
) == 0)
208 // Return the output section to use for section NAME with type TYPE
209 // and section flags FLAGS.
212 Layout::get_output_section(const char* name
, Stringpool::Key name_key
,
213 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
)
215 // We should ignore some flags.
216 flags
&= ~ (elfcpp::SHF_INFO_LINK
217 | elfcpp::SHF_LINK_ORDER
220 | elfcpp::SHF_STRINGS
);
222 const Key
key(name_key
, std::make_pair(type
, flags
));
223 const std::pair
<Key
, Output_section
*> v(key
, NULL
);
224 std::pair
<Section_name_map::iterator
, bool> ins(
225 this->section_name_map_
.insert(v
));
228 return ins
.first
->second
;
231 // This is the first time we've seen this name/type/flags
233 Output_section
* os
= this->make_output_section(name
, type
, flags
);
234 ins
.first
->second
= os
;
239 // Return the output section to use for input section SHNDX, with name
240 // NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
241 // index of a relocation section which applies to this section, or 0
242 // if none, or -1U if more than one. RELOC_TYPE is the type of the
243 // relocation section if there is one. Set *OFF to the offset of this
244 // input section without the output section. Return NULL if the
245 // section should be discarded. Set *OFF to -1 if the section
246 // contents should not be written directly to the output file, but
247 // will instead receive special handling.
249 template<int size
, bool big_endian
>
251 Layout::layout(Sized_relobj
<size
, big_endian
>* object
, unsigned int shndx
,
252 const char* name
, const elfcpp::Shdr
<size
, big_endian
>& shdr
,
253 unsigned int reloc_shndx
, unsigned int, off_t
* off
)
255 if (!this->include_section(object
, name
, shdr
))
258 // If we are not doing a relocateable link, choose the name to use
259 // for the output section.
260 size_t len
= strlen(name
);
261 if (!parameters
->output_is_object())
262 name
= Layout::output_section_name(name
, &len
);
264 // FIXME: Handle SHF_OS_NONCONFORMING here.
266 // Canonicalize the section name.
267 Stringpool::Key name_key
;
268 name
= this->namepool_
.add_prefix(name
, len
, &name_key
);
270 // Find the output section. The output section is selected based on
271 // the section name, type, and flags.
272 Output_section
* os
= this->get_output_section(name
, name_key
,
274 shdr
.get_sh_flags());
276 // FIXME: Handle SHF_LINK_ORDER somewhere.
278 *off
= os
->add_input_section(object
, shndx
, name
, shdr
, reloc_shndx
);
283 // Special GNU handling of sections name .eh_frame. They will
284 // normally hold exception frame data as defined by the C++ ABI
285 // (http://codesourcery.com/cxx-abi/).
287 template<int size
, bool big_endian
>
289 Layout::layout_eh_frame(Sized_relobj
<size
, big_endian
>* object
,
290 const unsigned char* symbols
,
292 const unsigned char* symbol_names
,
293 off_t symbol_names_size
,
295 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
296 unsigned int reloc_shndx
, unsigned int reloc_type
,
299 gold_assert(shdr
.get_sh_type() == elfcpp::SHT_PROGBITS
);
300 gold_assert(shdr
.get_sh_flags() == elfcpp::SHF_ALLOC
);
302 Stringpool::Key name_key
;
303 const char* name
= this->namepool_
.add(".eh_frame", false, &name_key
);
305 Output_section
* os
= this->get_output_section(name
, name_key
,
306 elfcpp::SHT_PROGBITS
,
309 if (this->eh_frame_section_
== NULL
)
311 this->eh_frame_section_
= os
;
312 this->eh_frame_data_
= new Eh_frame();
313 os
->add_output_section_data(this->eh_frame_data_
);
315 if (this->options_
.create_eh_frame_hdr())
317 Stringpool::Key hdr_name_key
;
318 const char* hdr_name
= this->namepool_
.add(".eh_frame_hdr",
321 Output_section
* hdr_os
=
322 this->get_output_section(hdr_name
, hdr_name_key
,
323 elfcpp::SHT_PROGBITS
,
326 Eh_frame_hdr
* hdr_posd
= new Eh_frame_hdr(os
, this->eh_frame_data_
);
327 hdr_os
->add_output_section_data(hdr_posd
);
329 hdr_os
->set_after_input_sections();
331 Output_segment
* hdr_oseg
=
332 new Output_segment(elfcpp::PT_GNU_EH_FRAME
, elfcpp::PF_R
);
333 this->segment_list_
.push_back(hdr_oseg
);
334 hdr_oseg
->add_output_section(hdr_os
, elfcpp::PF_R
);
336 this->eh_frame_data_
->set_eh_frame_hdr(hdr_posd
);
340 gold_assert(this->eh_frame_section_
== os
);
342 if (this->eh_frame_data_
->add_ehframe_input_section(object
,
353 // We couldn't handle this .eh_frame section for some reason.
354 // Add it as a normal section.
355 *off
= os
->add_input_section(object
, shndx
, name
, shdr
, reloc_shndx
);
361 // Add POSD to an output section using NAME, TYPE, and FLAGS.
364 Layout::add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
365 elfcpp::Elf_Xword flags
,
366 Output_section_data
* posd
)
368 // Canonicalize the name.
369 Stringpool::Key name_key
;
370 name
= this->namepool_
.add(name
, true, &name_key
);
372 Output_section
* os
= this->get_output_section(name
, name_key
, type
, flags
);
373 os
->add_output_section_data(posd
);
376 // Map section flags to segment flags.
379 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags
)
381 elfcpp::Elf_Word ret
= elfcpp::PF_R
;
382 if ((flags
& elfcpp::SHF_WRITE
) != 0)
384 if ((flags
& elfcpp::SHF_EXECINSTR
) != 0)
389 // Make a new Output_section, and attach it to segments as
393 Layout::make_output_section(const char* name
, elfcpp::Elf_Word type
,
394 elfcpp::Elf_Xword flags
)
396 Output_section
* os
= new Output_section(this->options_
, name
, type
, flags
);
397 this->section_list_
.push_back(os
);
399 if ((flags
& elfcpp::SHF_ALLOC
) == 0)
400 this->unattached_section_list_
.push_back(os
);
403 // This output section goes into a PT_LOAD segment.
405 elfcpp::Elf_Word seg_flags
= Layout::section_flags_to_segment(flags
);
407 // The only thing we really care about for PT_LOAD segments is
408 // whether or not they are writable, so that is how we search
409 // for them. People who need segments sorted on some other
410 // basis will have to wait until we implement a mechanism for
411 // them to describe the segments they want.
413 Segment_list::const_iterator p
;
414 for (p
= this->segment_list_
.begin();
415 p
!= this->segment_list_
.end();
418 if ((*p
)->type() == elfcpp::PT_LOAD
419 && ((*p
)->flags() & elfcpp::PF_W
) == (seg_flags
& elfcpp::PF_W
))
421 (*p
)->add_output_section(os
, seg_flags
);
426 if (p
== this->segment_list_
.end())
428 Output_segment
* oseg
= new Output_segment(elfcpp::PT_LOAD
,
430 this->segment_list_
.push_back(oseg
);
431 oseg
->add_output_section(os
, seg_flags
);
434 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
436 if (type
== elfcpp::SHT_NOTE
)
438 // See if we already have an equivalent PT_NOTE segment.
439 for (p
= this->segment_list_
.begin();
440 p
!= segment_list_
.end();
443 if ((*p
)->type() == elfcpp::PT_NOTE
444 && (((*p
)->flags() & elfcpp::PF_W
)
445 == (seg_flags
& elfcpp::PF_W
)))
447 (*p
)->add_output_section(os
, seg_flags
);
452 if (p
== this->segment_list_
.end())
454 Output_segment
* oseg
= new Output_segment(elfcpp::PT_NOTE
,
456 this->segment_list_
.push_back(oseg
);
457 oseg
->add_output_section(os
, seg_flags
);
461 // If we see a loadable SHF_TLS section, we create a PT_TLS
462 // segment. There can only be one such segment.
463 if ((flags
& elfcpp::SHF_TLS
) != 0)
465 if (this->tls_segment_
== NULL
)
467 this->tls_segment_
= new Output_segment(elfcpp::PT_TLS
,
469 this->segment_list_
.push_back(this->tls_segment_
);
471 this->tls_segment_
->add_output_section(os
, seg_flags
);
478 // Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
479 // is whether we saw a .note.GNU-stack section in the object file.
480 // GNU_STACK_FLAGS is the section flags. The flags give the
481 // protection required for stack memory. We record this in an
482 // executable as a PT_GNU_STACK segment. If an object file does not
483 // have a .note.GNU-stack segment, we must assume that it is an old
484 // object. On some targets that will force an executable stack.
487 Layout::layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
)
490 this->input_without_gnu_stack_note_
= true;
493 this->input_with_gnu_stack_note_
= true;
494 if ((gnu_stack_flags
& elfcpp::SHF_EXECINSTR
) != 0)
495 this->input_requires_executable_stack_
= true;
499 // Create the dynamic sections which are needed before we read the
503 Layout::create_initial_dynamic_sections(const Input_objects
* input_objects
,
504 Symbol_table
* symtab
)
506 if (parameters
->doing_static_link())
509 const char* dynamic_name
= this->namepool_
.add(".dynamic", false, NULL
);
510 this->dynamic_section_
= this->make_output_section(dynamic_name
,
513 | elfcpp::SHF_WRITE
));
515 symtab
->define_in_output_data(input_objects
->target(), "_DYNAMIC", NULL
,
516 this->dynamic_section_
, 0, 0,
517 elfcpp::STT_OBJECT
, elfcpp::STB_LOCAL
,
518 elfcpp::STV_HIDDEN
, 0, false, false);
520 this->dynamic_data_
= new Output_data_dynamic(&this->dynpool_
);
522 this->dynamic_section_
->add_output_section_data(this->dynamic_data_
);
525 // For each output section whose name can be represented as C symbol,
526 // define __start and __stop symbols for the section. This is a GNU
530 Layout::define_section_symbols(Symbol_table
* symtab
, const Target
* target
)
532 for (Section_list::const_iterator p
= this->section_list_
.begin();
533 p
!= this->section_list_
.end();
536 const char* const name
= (*p
)->name();
537 if (name
[strspn(name
,
539 "ABCDEFGHIJKLMNOPWRSTUVWXYZ"
540 "abcdefghijklmnopqrstuvwxyz"
544 const std::string
name_string(name
);
545 const std::string
start_name("__start_" + name_string
);
546 const std::string
stop_name("__stop_" + name_string
);
548 symtab
->define_in_output_data(target
,
558 false, // offset_is_from_end
559 false); // only_if_ref
561 symtab
->define_in_output_data(target
,
571 true, // offset_is_from_end
572 false); // only_if_ref
577 // Find the first read-only PT_LOAD segment, creating one if
581 Layout::find_first_load_seg()
583 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
584 p
!= this->segment_list_
.end();
587 if ((*p
)->type() == elfcpp::PT_LOAD
588 && ((*p
)->flags() & elfcpp::PF_R
) != 0
589 && ((*p
)->flags() & elfcpp::PF_W
) == 0)
593 Output_segment
* load_seg
= new Output_segment(elfcpp::PT_LOAD
, elfcpp::PF_R
);
594 this->segment_list_
.push_back(load_seg
);
598 // Finalize the layout. When this is called, we have created all the
599 // output sections and all the output segments which are based on
600 // input sections. We have several things to do, and we have to do
601 // them in the right order, so that we get the right results correctly
604 // 1) Finalize the list of output segments and create the segment
607 // 2) Finalize the dynamic symbol table and associated sections.
609 // 3) Determine the final file offset of all the output segments.
611 // 4) Determine the final file offset of all the SHF_ALLOC output
614 // 5) Create the symbol table sections and the section name table
617 // 6) Finalize the symbol table: set symbol values to their final
618 // value and make a final determination of which symbols are going
619 // into the output symbol table.
621 // 7) Create the section table header.
623 // 8) Determine the final file offset of all the output sections which
624 // are not SHF_ALLOC, including the section table header.
626 // 9) Finalize the ELF file header.
628 // This function returns the size of the output file.
631 Layout::finalize(const Input_objects
* input_objects
, Symbol_table
* symtab
)
633 Target
* const target
= input_objects
->target();
635 target
->finalize_sections(this);
637 this->create_gold_note();
638 this->create_executable_stack_info(target
);
640 Output_segment
* phdr_seg
= NULL
;
641 if (!parameters
->doing_static_link())
643 // There was a dynamic object in the link. We need to create
644 // some information for the dynamic linker.
646 // Create the PT_PHDR segment which will hold the program
648 phdr_seg
= new Output_segment(elfcpp::PT_PHDR
, elfcpp::PF_R
);
649 this->segment_list_
.push_back(phdr_seg
);
651 // Create the dynamic symbol table, including the hash table.
652 Output_section
* dynstr
;
653 std::vector
<Symbol
*> dynamic_symbols
;
654 unsigned int local_dynamic_count
;
656 this->create_dynamic_symtab(target
, symtab
, &dynstr
,
657 &local_dynamic_count
, &dynamic_symbols
,
660 // Create the .interp section to hold the name of the
661 // interpreter, and put it in a PT_INTERP segment.
662 if (!parameters
->output_is_shared())
663 this->create_interp(target
);
665 // Finish the .dynamic section to hold the dynamic data, and put
666 // it in a PT_DYNAMIC segment.
667 this->finish_dynamic_section(input_objects
, symtab
);
669 // We should have added everything we need to the dynamic string
671 this->dynpool_
.set_string_offsets();
673 // Create the version sections. We can't do this until the
674 // dynamic string table is complete.
675 this->create_version_sections(&versions
, symtab
, local_dynamic_count
,
676 dynamic_symbols
, dynstr
);
679 // FIXME: Handle PT_GNU_STACK.
681 Output_segment
* load_seg
= this->find_first_load_seg();
683 // Lay out the segment headers.
684 Output_segment_headers
* segment_headers
;
685 segment_headers
= new Output_segment_headers(this->segment_list_
);
686 load_seg
->add_initial_output_data(segment_headers
);
687 this->special_output_list_
.push_back(segment_headers
);
688 if (phdr_seg
!= NULL
)
689 phdr_seg
->add_initial_output_data(segment_headers
);
691 // Lay out the file header.
692 Output_file_header
* file_header
;
693 file_header
= new Output_file_header(target
, symtab
, segment_headers
);
694 load_seg
->add_initial_output_data(file_header
);
695 this->special_output_list_
.push_back(file_header
);
697 // We set the output section indexes in set_segment_offsets and
698 // set_section_indexes.
699 unsigned int shndx
= 1;
701 // Set the file offsets of all the segments, and all the sections
703 off_t off
= this->set_segment_offsets(target
, load_seg
, &shndx
);
705 // Create the symbol table sections.
706 this->create_symtab_sections(input_objects
, symtab
, &off
);
708 // Create the .shstrtab section.
709 Output_section
* shstrtab_section
= this->create_shstrtab();
711 // Set the file offsets of all the non-data sections which don't
712 // have to wait for the input sections.
713 off
= this->set_section_offsets(off
, BEFORE_INPUT_SECTIONS_PASS
);
715 // Now that all sections have been created, set the section indexes.
716 shndx
= this->set_section_indexes(shndx
);
718 // Create the section table header.
719 this->create_shdrs(&off
);
721 file_header
->set_section_info(this->section_headers_
, shstrtab_section
);
723 // Now we know exactly where everything goes in the output file
724 // (except for non-allocated sections which require postprocessing).
725 Output_data::layout_complete();
727 this->output_file_size_
= off
;
732 // Create a .note section for an executable or shared library. This
733 // records the version of gold used to create the binary.
736 Layout::create_gold_note()
738 if (parameters
->output_is_object())
741 // Authorities all agree that the values in a .note field should
742 // be aligned on 4-byte boundaries for 32-bit binaries. However,
743 // they differ on what the alignment is for 64-bit binaries.
744 // The GABI says unambiguously they take 8-byte alignment:
745 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
746 // Other documentation says alignment should always be 4 bytes:
747 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
748 // GNU ld and GNU readelf both support the latter (at least as of
749 // version 2.16.91), and glibc always generates the latter for
750 // .note.ABI-tag (as of version 1.6), so that's the one we go with
752 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
753 const int size
= parameters
->get_size();
758 // The contents of the .note section.
759 const char* name
= "GNU";
760 std::string
desc(std::string("gold ") + gold::get_version_string());
761 size_t namesz
= strlen(name
) + 1;
762 size_t aligned_namesz
= align_address(namesz
, size
/ 8);
763 size_t descsz
= desc
.length() + 1;
764 size_t aligned_descsz
= align_address(descsz
, size
/ 8);
765 const int note_type
= 4;
767 size_t notesz
= 3 * (size
/ 8) + aligned_namesz
+ aligned_descsz
;
769 unsigned char buffer
[128];
770 gold_assert(sizeof buffer
>= notesz
);
771 memset(buffer
, 0, notesz
);
773 bool is_big_endian
= parameters
->is_big_endian();
779 elfcpp::Swap
<32, false>::writeval(buffer
, namesz
);
780 elfcpp::Swap
<32, false>::writeval(buffer
+ 4, descsz
);
781 elfcpp::Swap
<32, false>::writeval(buffer
+ 8, note_type
);
785 elfcpp::Swap
<32, true>::writeval(buffer
, namesz
);
786 elfcpp::Swap
<32, true>::writeval(buffer
+ 4, descsz
);
787 elfcpp::Swap
<32, true>::writeval(buffer
+ 8, note_type
);
794 elfcpp::Swap
<64, false>::writeval(buffer
, namesz
);
795 elfcpp::Swap
<64, false>::writeval(buffer
+ 8, descsz
);
796 elfcpp::Swap
<64, false>::writeval(buffer
+ 16, note_type
);
800 elfcpp::Swap
<64, true>::writeval(buffer
, namesz
);
801 elfcpp::Swap
<64, true>::writeval(buffer
+ 8, descsz
);
802 elfcpp::Swap
<64, true>::writeval(buffer
+ 16, note_type
);
808 memcpy(buffer
+ 3 * (size
/ 8), name
, namesz
);
809 memcpy(buffer
+ 3 * (size
/ 8) + aligned_namesz
, desc
.data(), descsz
);
811 const char* note_name
= this->namepool_
.add(".note", false, NULL
);
812 Output_section
* os
= this->make_output_section(note_name
,
815 Output_section_data
* posd
= new Output_data_const(buffer
, notesz
,
817 os
->add_output_section_data(posd
);
820 // Record whether the stack should be executable. This can be set
821 // from the command line using the -z execstack or -z noexecstack
822 // options. Otherwise, if any input file has a .note.GNU-stack
823 // section with the SHF_EXECINSTR flag set, the stack should be
824 // executable. Otherwise, if at least one input file a
825 // .note.GNU-stack section, and some input file has no .note.GNU-stack
826 // section, we use the target default for whether the stack should be
827 // executable. Otherwise, we don't generate a stack note. When
828 // generating a object file, we create a .note.GNU-stack section with
829 // the appropriate marking. When generating an executable or shared
830 // library, we create a PT_GNU_STACK segment.
833 Layout::create_executable_stack_info(const Target
* target
)
835 bool is_stack_executable
;
836 if (this->options_
.is_execstack_set())
837 is_stack_executable
= this->options_
.is_stack_executable();
838 else if (!this->input_with_gnu_stack_note_
)
842 if (this->input_requires_executable_stack_
)
843 is_stack_executable
= true;
844 else if (this->input_without_gnu_stack_note_
)
845 is_stack_executable
= target
->is_default_stack_executable();
847 is_stack_executable
= false;
850 if (parameters
->output_is_object())
852 const char* name
= this->namepool_
.add(".note.GNU-stack", false, NULL
);
853 elfcpp::Elf_Xword flags
= 0;
854 if (is_stack_executable
)
855 flags
|= elfcpp::SHF_EXECINSTR
;
856 this->make_output_section(name
, elfcpp::SHT_PROGBITS
, flags
);
860 int flags
= elfcpp::PF_R
| elfcpp::PF_W
;
861 if (is_stack_executable
)
862 flags
|= elfcpp::PF_X
;
863 Output_segment
* oseg
= new Output_segment(elfcpp::PT_GNU_STACK
, flags
);
864 this->segment_list_
.push_back(oseg
);
868 // Return whether SEG1 should be before SEG2 in the output file. This
869 // is based entirely on the segment type and flags. When this is
870 // called the segment addresses has normally not yet been set.
873 Layout::segment_precedes(const Output_segment
* seg1
,
874 const Output_segment
* seg2
)
876 elfcpp::Elf_Word type1
= seg1
->type();
877 elfcpp::Elf_Word type2
= seg2
->type();
879 // The single PT_PHDR segment is required to precede any loadable
880 // segment. We simply make it always first.
881 if (type1
== elfcpp::PT_PHDR
)
883 gold_assert(type2
!= elfcpp::PT_PHDR
);
886 if (type2
== elfcpp::PT_PHDR
)
889 // The single PT_INTERP segment is required to precede any loadable
890 // segment. We simply make it always second.
891 if (type1
== elfcpp::PT_INTERP
)
893 gold_assert(type2
!= elfcpp::PT_INTERP
);
896 if (type2
== elfcpp::PT_INTERP
)
899 // We then put PT_LOAD segments before any other segments.
900 if (type1
== elfcpp::PT_LOAD
&& type2
!= elfcpp::PT_LOAD
)
902 if (type2
== elfcpp::PT_LOAD
&& type1
!= elfcpp::PT_LOAD
)
905 // We put the PT_TLS segment last, because that is where the dynamic
906 // linker expects to find it (this is just for efficiency; other
907 // positions would also work correctly).
908 if (type1
== elfcpp::PT_TLS
&& type2
!= elfcpp::PT_TLS
)
910 if (type2
== elfcpp::PT_TLS
&& type1
!= elfcpp::PT_TLS
)
913 const elfcpp::Elf_Word flags1
= seg1
->flags();
914 const elfcpp::Elf_Word flags2
= seg2
->flags();
916 // The order of non-PT_LOAD segments is unimportant. We simply sort
917 // by the numeric segment type and flags values. There should not
918 // be more than one segment with the same type and flags.
919 if (type1
!= elfcpp::PT_LOAD
)
922 return type1
< type2
;
923 gold_assert(flags1
!= flags2
);
924 return flags1
< flags2
;
927 // We sort PT_LOAD segments based on the flags. Readonly segments
928 // come before writable segments. Then executable segments come
929 // before non-executable segments. Then the unlikely case of a
930 // non-readable segment comes before the normal case of a readable
931 // segment. If there are multiple segments with the same type and
932 // flags, we require that the address be set, and we sort by
933 // virtual address and then physical address.
934 if ((flags1
& elfcpp::PF_W
) != (flags2
& elfcpp::PF_W
))
935 return (flags1
& elfcpp::PF_W
) == 0;
936 if ((flags1
& elfcpp::PF_X
) != (flags2
& elfcpp::PF_X
))
937 return (flags1
& elfcpp::PF_X
) != 0;
938 if ((flags1
& elfcpp::PF_R
) != (flags2
& elfcpp::PF_R
))
939 return (flags1
& elfcpp::PF_R
) == 0;
941 uint64_t vaddr1
= seg1
->vaddr();
942 uint64_t vaddr2
= seg2
->vaddr();
943 if (vaddr1
!= vaddr2
)
944 return vaddr1
< vaddr2
;
946 uint64_t paddr1
= seg1
->paddr();
947 uint64_t paddr2
= seg2
->paddr();
948 gold_assert(paddr1
!= paddr2
);
949 return paddr1
< paddr2
;
952 // Set the file offsets of all the segments, and all the sections they
953 // contain. They have all been created. LOAD_SEG must be be laid out
954 // first. Return the offset of the data to follow.
957 Layout::set_segment_offsets(const Target
* target
, Output_segment
* load_seg
,
958 unsigned int *pshndx
)
960 // Sort them into the final order.
961 std::sort(this->segment_list_
.begin(), this->segment_list_
.end(),
962 Layout::Compare_segments());
964 // Find the PT_LOAD segments, and set their addresses and offsets
965 // and their section's addresses and offsets.
967 if (options_
.user_set_text_segment_address())
968 addr
= options_
.text_segment_address();
970 addr
= target
->default_text_segment_address();
972 bool was_readonly
= false;
973 for (Segment_list::iterator p
= this->segment_list_
.begin();
974 p
!= this->segment_list_
.end();
977 if ((*p
)->type() == elfcpp::PT_LOAD
)
979 if (load_seg
!= NULL
&& load_seg
!= *p
)
983 // If the last segment was readonly, and this one is not,
984 // then skip the address forward one page, maintaining the
985 // same position within the page. This lets us store both
986 // segments overlapping on a single page in the file, but
987 // the loader will put them on different pages in memory.
989 uint64_t orig_addr
= addr
;
990 uint64_t orig_off
= off
;
992 uint64_t aligned_addr
= addr
;
993 uint64_t abi_pagesize
= target
->abi_pagesize();
995 // FIXME: This should depend on the -n and -N options.
996 (*p
)->set_minimum_addralign(target
->common_pagesize());
998 if (was_readonly
&& ((*p
)->flags() & elfcpp::PF_W
) != 0)
1000 uint64_t align
= (*p
)->addralign();
1002 addr
= align_address(addr
, align
);
1003 aligned_addr
= addr
;
1004 if ((addr
& (abi_pagesize
- 1)) != 0)
1005 addr
= addr
+ abi_pagesize
;
1008 unsigned int shndx_hold
= *pshndx
;
1009 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1010 uint64_t new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
1012 // Now that we know the size of this segment, we may be able
1013 // to save a page in memory, at the cost of wasting some
1014 // file space, by instead aligning to the start of a new
1015 // page. Here we use the real machine page size rather than
1016 // the ABI mandated page size.
1018 if (aligned_addr
!= addr
)
1020 uint64_t common_pagesize
= target
->common_pagesize();
1021 uint64_t first_off
= (common_pagesize
1023 & (common_pagesize
- 1)));
1024 uint64_t last_off
= new_addr
& (common_pagesize
- 1);
1027 && ((aligned_addr
& ~ (common_pagesize
- 1))
1028 != (new_addr
& ~ (common_pagesize
- 1)))
1029 && first_off
+ last_off
<= common_pagesize
)
1031 *pshndx
= shndx_hold
;
1032 addr
= align_address(aligned_addr
, common_pagesize
);
1033 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1034 new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
1040 if (((*p
)->flags() & elfcpp::PF_W
) == 0)
1041 was_readonly
= true;
1045 // Handle the non-PT_LOAD segments, setting their offsets from their
1046 // section's offsets.
1047 for (Segment_list::iterator p
= this->segment_list_
.begin();
1048 p
!= this->segment_list_
.end();
1051 if ((*p
)->type() != elfcpp::PT_LOAD
)
1058 // Set the file offset of all the sections not associated with a
1062 Layout::set_section_offsets(off_t off
, Layout::Section_offset_pass pass
)
1064 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1065 p
!= this->unattached_section_list_
.end();
1068 // The symtab section is handled in create_symtab_sections.
1069 if (*p
== this->symtab_section_
)
1072 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1073 && (*p
)->after_input_sections())
1075 else if (pass
== AFTER_INPUT_SECTIONS_PASS
1076 && (!(*p
)->after_input_sections()
1077 || (*p
)->type() == elfcpp::SHT_STRTAB
))
1079 else if (pass
== STRTAB_AFTER_INPUT_SECTIONS_PASS
1080 && (!(*p
)->after_input_sections()
1081 || (*p
)->type() != elfcpp::SHT_STRTAB
))
1084 off
= align_address(off
, (*p
)->addralign());
1085 (*p
)->set_file_offset(off
);
1086 (*p
)->finalize_data_size();
1087 off
+= (*p
)->data_size();
1092 // Allow any section not associated with a segment to change its
1093 // output section name at the last minute.
1096 Layout::modify_section_names()
1098 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1099 p
!= this->unattached_section_list_
.end();
1101 if ((*p
)->maybe_modify_output_section_name())
1102 this->namepool_
.add((*p
)->name(), true, NULL
);
1105 // Set the section indexes of all the sections not associated with a
1109 Layout::set_section_indexes(unsigned int shndx
)
1111 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1112 p
!= this->unattached_section_list_
.end();
1115 (*p
)->set_out_shndx(shndx
);
1121 // Create the symbol table sections. Here we also set the final
1122 // values of the symbols. At this point all the loadable sections are
1126 Layout::create_symtab_sections(const Input_objects
* input_objects
,
1127 Symbol_table
* symtab
,
1132 if (parameters
->get_size() == 32)
1134 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1137 else if (parameters
->get_size() == 64)
1139 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1146 off
= align_address(off
, align
);
1147 off_t startoff
= off
;
1149 // Save space for the dummy symbol at the start of the section. We
1150 // never bother to write this out--it will just be left as zero.
1152 unsigned int local_symbol_index
= 1;
1154 // Add STT_SECTION symbols for each Output section which needs one.
1155 for (Section_list::iterator p
= this->section_list_
.begin();
1156 p
!= this->section_list_
.end();
1159 if (!(*p
)->needs_symtab_index())
1160 (*p
)->set_symtab_index(-1U);
1163 (*p
)->set_symtab_index(local_symbol_index
);
1164 ++local_symbol_index
;
1169 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1170 p
!= input_objects
->relobj_end();
1173 Task_lock_obj
<Object
> tlo(**p
);
1174 unsigned int index
= (*p
)->finalize_local_symbols(local_symbol_index
,
1177 off
+= (index
- local_symbol_index
) * symsize
;
1178 local_symbol_index
= index
;
1181 unsigned int local_symcount
= local_symbol_index
;
1182 gold_assert(local_symcount
* symsize
== off
- startoff
);
1185 size_t dyn_global_index
;
1187 if (this->dynsym_section_
== NULL
)
1190 dyn_global_index
= 0;
1195 dyn_global_index
= this->dynsym_section_
->info();
1196 off_t locsize
= dyn_global_index
* this->dynsym_section_
->entsize();
1197 dynoff
= this->dynsym_section_
->offset() + locsize
;
1198 dyncount
= (this->dynsym_section_
->data_size() - locsize
) / symsize
;
1199 gold_assert(static_cast<off_t
>(dyncount
* symsize
)
1200 == this->dynsym_section_
->data_size() - locsize
);
1203 off
= symtab
->finalize(local_symcount
, off
, dynoff
, dyn_global_index
,
1204 dyncount
, &this->sympool_
);
1206 if (!parameters
->strip_all())
1208 this->sympool_
.set_string_offsets();
1210 const char* symtab_name
= this->namepool_
.add(".symtab", false, NULL
);
1211 Output_section
* osymtab
= this->make_output_section(symtab_name
,
1214 this->symtab_section_
= osymtab
;
1216 Output_section_data
* pos
= new Output_data_fixed_space(off
- startoff
,
1218 osymtab
->add_output_section_data(pos
);
1220 const char* strtab_name
= this->namepool_
.add(".strtab", false, NULL
);
1221 Output_section
* ostrtab
= this->make_output_section(strtab_name
,
1225 Output_section_data
* pstr
= new Output_data_strtab(&this->sympool_
);
1226 ostrtab
->add_output_section_data(pstr
);
1228 osymtab
->set_file_offset(startoff
);
1229 osymtab
->finalize_data_size();
1230 osymtab
->set_link_section(ostrtab
);
1231 osymtab
->set_info(local_symcount
);
1232 osymtab
->set_entsize(symsize
);
1238 // Create the .shstrtab section, which holds the names of the
1239 // sections. At the time this is called, we have created all the
1240 // output sections except .shstrtab itself.
1243 Layout::create_shstrtab()
1245 // FIXME: We don't need to create a .shstrtab section if we are
1246 // stripping everything.
1248 const char* name
= this->namepool_
.add(".shstrtab", false, NULL
);
1250 Output_section
* os
= this->make_output_section(name
, elfcpp::SHT_STRTAB
, 0);
1252 // We can't write out this section until we've set all the section
1253 // names, and we don't set the names of compressed output sections
1254 // until relocations are complete.
1255 os
->set_after_input_sections();
1257 Output_section_data
* posd
= new Output_data_strtab(&this->namepool_
);
1258 os
->add_output_section_data(posd
);
1263 // Create the section headers. SIZE is 32 or 64. OFF is the file
1267 Layout::create_shdrs(off_t
* poff
)
1269 Output_section_headers
* oshdrs
;
1270 oshdrs
= new Output_section_headers(this,
1271 &this->segment_list_
,
1272 &this->unattached_section_list_
,
1274 off_t off
= align_address(*poff
, oshdrs
->addralign());
1275 oshdrs
->set_address_and_file_offset(0, off
);
1276 off
+= oshdrs
->data_size();
1278 this->section_headers_
= oshdrs
;
1281 // Create the dynamic symbol table.
1284 Layout::create_dynamic_symtab(const Target
* target
, Symbol_table
* symtab
,
1285 Output_section
**pdynstr
,
1286 unsigned int* plocal_dynamic_count
,
1287 std::vector
<Symbol
*>* pdynamic_symbols
,
1288 Versions
* pversions
)
1290 // Count all the symbols in the dynamic symbol table, and set the
1291 // dynamic symbol indexes.
1293 // Skip symbol 0, which is always all zeroes.
1294 unsigned int index
= 1;
1296 // Add STT_SECTION symbols for each Output section which needs one.
1297 for (Section_list::iterator p
= this->section_list_
.begin();
1298 p
!= this->section_list_
.end();
1301 if (!(*p
)->needs_dynsym_index())
1302 (*p
)->set_dynsym_index(-1U);
1305 (*p
)->set_dynsym_index(index
);
1310 // FIXME: Some targets apparently require local symbols in the
1311 // dynamic symbol table. Here is where we will have to count them,
1312 // and set the dynamic symbol indexes, and add the names to
1315 unsigned int local_symcount
= index
;
1316 *plocal_dynamic_count
= local_symcount
;
1318 // FIXME: We have to tell set_dynsym_indexes whether the
1319 // -E/--export-dynamic option was used.
1320 index
= symtab
->set_dynsym_indexes(target
, index
, pdynamic_symbols
,
1321 &this->dynpool_
, pversions
);
1325 const int size
= parameters
->get_size();
1328 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1331 else if (size
== 64)
1333 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1339 // Create the dynamic symbol table section.
1341 const char* dynsym_name
= this->namepool_
.add(".dynsym", false, NULL
);
1342 Output_section
* dynsym
= this->make_output_section(dynsym_name
,
1346 Output_section_data
* odata
= new Output_data_fixed_space(index
* symsize
,
1348 dynsym
->add_output_section_data(odata
);
1350 dynsym
->set_info(local_symcount
);
1351 dynsym
->set_entsize(symsize
);
1352 dynsym
->set_addralign(align
);
1354 this->dynsym_section_
= dynsym
;
1356 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1357 odyn
->add_section_address(elfcpp::DT_SYMTAB
, dynsym
);
1358 odyn
->add_constant(elfcpp::DT_SYMENT
, symsize
);
1360 // Create the dynamic string table section.
1362 const char* dynstr_name
= this->namepool_
.add(".dynstr", false, NULL
);
1363 Output_section
* dynstr
= this->make_output_section(dynstr_name
,
1367 Output_section_data
* strdata
= new Output_data_strtab(&this->dynpool_
);
1368 dynstr
->add_output_section_data(strdata
);
1370 dynsym
->set_link_section(dynstr
);
1371 this->dynamic_section_
->set_link_section(dynstr
);
1373 odyn
->add_section_address(elfcpp::DT_STRTAB
, dynstr
);
1374 odyn
->add_section_size(elfcpp::DT_STRSZ
, dynstr
);
1378 // Create the hash tables.
1380 // FIXME: We need an option to create a GNU hash table.
1382 unsigned char* phash
;
1383 unsigned int hashlen
;
1384 Dynobj::create_elf_hash_table(*pdynamic_symbols
, local_symcount
,
1387 const char* hash_name
= this->namepool_
.add(".hash", false, NULL
);
1388 Output_section
* hashsec
= this->make_output_section(hash_name
,
1392 Output_section_data
* hashdata
= new Output_data_const_buffer(phash
,
1395 hashsec
->add_output_section_data(hashdata
);
1397 hashsec
->set_link_section(dynsym
);
1398 hashsec
->set_entsize(4);
1400 odyn
->add_section_address(elfcpp::DT_HASH
, hashsec
);
1403 // Create the version sections.
1406 Layout::create_version_sections(const Versions
* versions
,
1407 const Symbol_table
* symtab
,
1408 unsigned int local_symcount
,
1409 const std::vector
<Symbol
*>& dynamic_symbols
,
1410 const Output_section
* dynstr
)
1412 if (!versions
->any_defs() && !versions
->any_needs())
1415 if (parameters
->get_size() == 32)
1417 if (parameters
->is_big_endian())
1419 #ifdef HAVE_TARGET_32_BIG
1420 this->sized_create_version_sections
1421 SELECT_SIZE_ENDIAN_NAME(32, true)(
1422 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1423 SELECT_SIZE_ENDIAN(32, true));
1430 #ifdef HAVE_TARGET_32_LITTLE
1431 this->sized_create_version_sections
1432 SELECT_SIZE_ENDIAN_NAME(32, false)(
1433 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1434 SELECT_SIZE_ENDIAN(32, false));
1440 else if (parameters
->get_size() == 64)
1442 if (parameters
->is_big_endian())
1444 #ifdef HAVE_TARGET_64_BIG
1445 this->sized_create_version_sections
1446 SELECT_SIZE_ENDIAN_NAME(64, true)(
1447 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1448 SELECT_SIZE_ENDIAN(64, true));
1455 #ifdef HAVE_TARGET_64_LITTLE
1456 this->sized_create_version_sections
1457 SELECT_SIZE_ENDIAN_NAME(64, false)(
1458 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1459 SELECT_SIZE_ENDIAN(64, false));
1469 // Create the version sections, sized version.
1471 template<int size
, bool big_endian
>
1473 Layout::sized_create_version_sections(
1474 const Versions
* versions
,
1475 const Symbol_table
* symtab
,
1476 unsigned int local_symcount
,
1477 const std::vector
<Symbol
*>& dynamic_symbols
,
1478 const Output_section
* dynstr
1481 const char* vname
= this->namepool_
.add(".gnu.version", false, NULL
);
1482 Output_section
* vsec
= this->make_output_section(vname
,
1483 elfcpp::SHT_GNU_versym
,
1486 unsigned char* vbuf
;
1488 versions
->symbol_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1489 symtab
, &this->dynpool_
, local_symcount
, dynamic_symbols
, &vbuf
, &vsize
1490 SELECT_SIZE_ENDIAN(size
, big_endian
));
1492 Output_section_data
* vdata
= new Output_data_const_buffer(vbuf
, vsize
, 2);
1494 vsec
->add_output_section_data(vdata
);
1495 vsec
->set_entsize(2);
1496 vsec
->set_link_section(this->dynsym_section_
);
1498 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1499 odyn
->add_section_address(elfcpp::DT_VERSYM
, vsec
);
1501 if (versions
->any_defs())
1503 const char* vdname
= this->namepool_
.add(".gnu.version_d", false, NULL
);
1504 Output_section
*vdsec
;
1505 vdsec
= this->make_output_section(vdname
, elfcpp::SHT_GNU_verdef
,
1508 unsigned char* vdbuf
;
1509 unsigned int vdsize
;
1510 unsigned int vdentries
;
1511 versions
->def_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1512 &this->dynpool_
, &vdbuf
, &vdsize
, &vdentries
1513 SELECT_SIZE_ENDIAN(size
, big_endian
));
1515 Output_section_data
* vddata
= new Output_data_const_buffer(vdbuf
,
1519 vdsec
->add_output_section_data(vddata
);
1520 vdsec
->set_link_section(dynstr
);
1521 vdsec
->set_info(vdentries
);
1523 odyn
->add_section_address(elfcpp::DT_VERDEF
, vdsec
);
1524 odyn
->add_constant(elfcpp::DT_VERDEFNUM
, vdentries
);
1527 if (versions
->any_needs())
1529 const char* vnname
= this->namepool_
.add(".gnu.version_r", false, NULL
);
1530 Output_section
* vnsec
;
1531 vnsec
= this->make_output_section(vnname
, elfcpp::SHT_GNU_verneed
,
1534 unsigned char* vnbuf
;
1535 unsigned int vnsize
;
1536 unsigned int vnentries
;
1537 versions
->need_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)
1538 (&this->dynpool_
, &vnbuf
, &vnsize
, &vnentries
1539 SELECT_SIZE_ENDIAN(size
, big_endian
));
1541 Output_section_data
* vndata
= new Output_data_const_buffer(vnbuf
,
1545 vnsec
->add_output_section_data(vndata
);
1546 vnsec
->set_link_section(dynstr
);
1547 vnsec
->set_info(vnentries
);
1549 odyn
->add_section_address(elfcpp::DT_VERNEED
, vnsec
);
1550 odyn
->add_constant(elfcpp::DT_VERNEEDNUM
, vnentries
);
1554 // Create the .interp section and PT_INTERP segment.
1557 Layout::create_interp(const Target
* target
)
1559 const char* interp
= this->options_
.dynamic_linker();
1562 interp
= target
->dynamic_linker();
1563 gold_assert(interp
!= NULL
);
1566 size_t len
= strlen(interp
) + 1;
1568 Output_section_data
* odata
= new Output_data_const(interp
, len
, 1);
1570 const char* interp_name
= this->namepool_
.add(".interp", false, NULL
);
1571 Output_section
* osec
= this->make_output_section(interp_name
,
1572 elfcpp::SHT_PROGBITS
,
1574 osec
->add_output_section_data(odata
);
1576 Output_segment
* oseg
= new Output_segment(elfcpp::PT_INTERP
, elfcpp::PF_R
);
1577 this->segment_list_
.push_back(oseg
);
1578 oseg
->add_initial_output_section(osec
, elfcpp::PF_R
);
1581 // Finish the .dynamic section and PT_DYNAMIC segment.
1584 Layout::finish_dynamic_section(const Input_objects
* input_objects
,
1585 const Symbol_table
* symtab
)
1587 Output_segment
* oseg
= new Output_segment(elfcpp::PT_DYNAMIC
,
1588 elfcpp::PF_R
| elfcpp::PF_W
);
1589 this->segment_list_
.push_back(oseg
);
1590 oseg
->add_initial_output_section(this->dynamic_section_
,
1591 elfcpp::PF_R
| elfcpp::PF_W
);
1593 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1595 for (Input_objects::Dynobj_iterator p
= input_objects
->dynobj_begin();
1596 p
!= input_objects
->dynobj_end();
1599 // FIXME: Handle --as-needed.
1600 odyn
->add_string(elfcpp::DT_NEEDED
, (*p
)->soname());
1603 // FIXME: Support --init and --fini.
1604 Symbol
* sym
= symtab
->lookup("_init");
1605 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1606 odyn
->add_symbol(elfcpp::DT_INIT
, sym
);
1608 sym
= symtab
->lookup("_fini");
1609 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1610 odyn
->add_symbol(elfcpp::DT_FINI
, sym
);
1612 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1614 // Add a DT_RPATH entry if needed.
1615 const General_options::Dir_list
& rpath(this->options_
.rpath());
1618 std::string rpath_val
;
1619 for (General_options::Dir_list::const_iterator p
= rpath
.begin();
1623 if (rpath_val
.empty())
1624 rpath_val
= p
->name();
1627 // Eliminate duplicates.
1628 General_options::Dir_list::const_iterator q
;
1629 for (q
= rpath
.begin(); q
!= p
; ++q
)
1630 if (q
->name() == p
->name())
1635 rpath_val
+= p
->name();
1640 odyn
->add_string(elfcpp::DT_RPATH
, rpath_val
);
1643 // Look for text segments that have dynamic relocations.
1644 bool have_textrel
= false;
1645 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
1646 p
!= this->segment_list_
.end();
1649 if (((*p
)->flags() & elfcpp::PF_W
) == 0
1650 && (*p
)->dynamic_reloc_count() > 0)
1652 have_textrel
= true;
1657 // Add a DT_FLAGS entry. We add it even if no flags are set so that
1658 // post-link tools can easily modify these flags if desired.
1659 unsigned int flags
= 0;
1661 flags
|= elfcpp::DF_TEXTREL
;
1662 odyn
->add_constant(elfcpp::DT_FLAGS
, flags
);
1665 // The mapping of .gnu.linkonce section names to real section names.
1667 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1668 const Layout::Linkonce_mapping
Layout::linkonce_mapping
[] =
1670 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1671 MAPPING_INIT("t", ".text"),
1672 MAPPING_INIT("r", ".rodata"),
1673 MAPPING_INIT("d", ".data"),
1674 MAPPING_INIT("b", ".bss"),
1675 MAPPING_INIT("s", ".sdata"),
1676 MAPPING_INIT("sb", ".sbss"),
1677 MAPPING_INIT("s2", ".sdata2"),
1678 MAPPING_INIT("sb2", ".sbss2"),
1679 MAPPING_INIT("wi", ".debug_info"),
1680 MAPPING_INIT("td", ".tdata"),
1681 MAPPING_INIT("tb", ".tbss"),
1682 MAPPING_INIT("lr", ".lrodata"),
1683 MAPPING_INIT("l", ".ldata"),
1684 MAPPING_INIT("lb", ".lbss"),
1688 const int Layout::linkonce_mapping_count
=
1689 sizeof(Layout::linkonce_mapping
) / sizeof(Layout::linkonce_mapping
[0]);
1691 // Return the name of the output section to use for a .gnu.linkonce
1692 // section. This is based on the default ELF linker script of the old
1693 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1694 // to ".text". Set *PLEN to the length of the name. *PLEN is
1695 // initialized to the length of NAME.
1698 Layout::linkonce_output_name(const char* name
, size_t *plen
)
1700 const char* s
= name
+ sizeof(".gnu.linkonce") - 1;
1704 const Linkonce_mapping
* plm
= linkonce_mapping
;
1705 for (int i
= 0; i
< linkonce_mapping_count
; ++i
, ++plm
)
1707 if (strncmp(s
, plm
->from
, plm
->fromlen
) == 0 && s
[plm
->fromlen
] == '.')
1716 // Choose the output section name to use given an input section name.
1717 // Set *PLEN to the length of the name. *PLEN is initialized to the
1721 Layout::output_section_name(const char* name
, size_t* plen
)
1723 if (Layout::is_linkonce(name
))
1725 // .gnu.linkonce sections are laid out as though they were named
1726 // for the sections are placed into.
1727 return Layout::linkonce_output_name(name
, plen
);
1730 // gcc 4.3 generates the following sorts of section names when it
1731 // needs a section name specific to a function:
1737 // .data.rel.local.FN
1739 // .data.rel.ro.local.FN
1746 // The GNU linker maps all of those to the part before the .FN,
1747 // except that .data.rel.local.FN is mapped to .data, and
1748 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
1749 // beginning with .data.rel.ro.local are grouped together.
1751 // For an anonymous namespace, the string FN can contain a '.'.
1753 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
1754 // GNU linker maps to .rodata.
1756 // The .data.rel.ro sections enable a security feature triggered by
1757 // the -z relro option. Section which need to be relocated at
1758 // program startup time but which may be readonly after startup are
1759 // grouped into .data.rel.ro. They are then put into a PT_GNU_RELRO
1760 // segment. The dynamic linker will make that segment writable,
1761 // perform relocations, and then make it read-only. FIXME: We do
1762 // not yet implement this optimization.
1764 // It is hard to handle this in a principled way.
1766 // These are the rules we follow:
1768 // If the section name has no initial '.', or no dot other than an
1769 // initial '.', we use the name unchanged (i.e., "mysection" and
1770 // ".text" are unchanged).
1772 // If the name starts with ".data.rel.ro" we use ".data.rel.ro".
1774 // Otherwise, we drop the second '.' and everything that comes after
1775 // it (i.e., ".text.XXX" becomes ".text").
1777 const char* s
= name
;
1781 const char* sdot
= strchr(s
, '.');
1785 const char* const data_rel_ro
= ".data.rel.ro";
1786 if (strncmp(name
, data_rel_ro
, strlen(data_rel_ro
)) == 0)
1788 *plen
= strlen(data_rel_ro
);
1792 *plen
= sdot
- name
;
1796 // Record the signature of a comdat section, and return whether to
1797 // include it in the link. If GROUP is true, this is a regular
1798 // section group. If GROUP is false, this is a group signature
1799 // derived from the name of a linkonce section. We want linkonce
1800 // signatures and group signatures to block each other, but we don't
1801 // want a linkonce signature to block another linkonce signature.
1804 Layout::add_comdat(const char* signature
, bool group
)
1806 std::string
sig(signature
);
1807 std::pair
<Signatures::iterator
, bool> ins(
1808 this->signatures_
.insert(std::make_pair(sig
, group
)));
1812 // This is the first time we've seen this signature.
1816 if (ins
.first
->second
)
1818 // We've already seen a real section group with this signature.
1823 // This is a real section group, and we've already seen a
1824 // linkonce section with this signature. Record that we've seen
1825 // a section group, and don't include this section group.
1826 ins
.first
->second
= true;
1831 // We've already seen a linkonce section and this is a linkonce
1832 // section. These don't block each other--this may be the same
1833 // symbol name with different section types.
1838 // Write out the Output_sections. Most won't have anything to write,
1839 // since most of the data will come from input sections which are
1840 // handled elsewhere. But some Output_sections do have Output_data.
1843 Layout::write_output_sections(Output_file
* of
) const
1845 for (Section_list::const_iterator p
= this->section_list_
.begin();
1846 p
!= this->section_list_
.end();
1849 if (!(*p
)->after_input_sections())
1854 // Write out data not associated with a section or the symbol table.
1857 Layout::write_data(const Symbol_table
* symtab
, Output_file
* of
) const
1859 if (!parameters
->strip_all())
1861 const Output_section
* symtab_section
= this->symtab_section_
;
1862 for (Section_list::const_iterator p
= this->section_list_
.begin();
1863 p
!= this->section_list_
.end();
1866 if ((*p
)->needs_symtab_index())
1868 gold_assert(symtab_section
!= NULL
);
1869 unsigned int index
= (*p
)->symtab_index();
1870 gold_assert(index
> 0 && index
!= -1U);
1871 off_t off
= (symtab_section
->offset()
1872 + index
* symtab_section
->entsize());
1873 symtab
->write_section_symbol(*p
, of
, off
);
1878 const Output_section
* dynsym_section
= this->dynsym_section_
;
1879 for (Section_list::const_iterator p
= this->section_list_
.begin();
1880 p
!= this->section_list_
.end();
1883 if ((*p
)->needs_dynsym_index())
1885 gold_assert(dynsym_section
!= NULL
);
1886 unsigned int index
= (*p
)->dynsym_index();
1887 gold_assert(index
> 0 && index
!= -1U);
1888 off_t off
= (dynsym_section
->offset()
1889 + index
* dynsym_section
->entsize());
1890 symtab
->write_section_symbol(*p
, of
, off
);
1894 // Write out the Output_data which are not in an Output_section.
1895 for (Data_list::const_iterator p
= this->special_output_list_
.begin();
1896 p
!= this->special_output_list_
.end();
1901 // Write out the Output_sections which can only be written after the
1902 // input sections are complete.
1905 Layout::write_sections_after_input_sections(Output_file
* of
)
1907 // Determine the final section offsets, and thus the final output
1908 // file size. Note we finalize the .shstrab last, to allow the
1909 // after_input_section sections to modify their section-names before
1911 off_t off
= this->output_file_size_
;
1912 off
= this->set_section_offsets(off
, AFTER_INPUT_SECTIONS_PASS
);
1914 // Determine the final section names as well (at least, for sections
1915 // that we haven't written yet).
1916 this->modify_section_names();
1918 // Now that we've finalized the names, we can finalize the shstrab.
1919 off
= this->set_section_offsets(off
, STRTAB_AFTER_INPUT_SECTIONS_PASS
);
1921 if (off
> this->output_file_size_
)
1924 this->output_file_size_
= off
;
1927 for (Section_list::const_iterator p
= this->section_list_
.begin();
1928 p
!= this->section_list_
.end();
1931 if ((*p
)->after_input_sections())
1935 for (Section_list::const_iterator p
= this->unattached_section_list_
.begin();
1936 p
!= this->unattached_section_list_
.end();
1939 if ((*p
)->after_input_sections())
1943 this->section_headers_
->write(of
);
1946 // Write_sections_task methods.
1948 // We can always run this task.
1950 Task::Is_runnable_type
1951 Write_sections_task::is_runnable(Workqueue
*)
1956 // We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
1959 class Write_sections_task::Write_sections_locker
: public Task_locker
1962 Write_sections_locker(Task_token
& output_sections_blocker
,
1963 Task_token
& final_blocker
,
1964 Workqueue
* workqueue
)
1965 : output_sections_block_(output_sections_blocker
, workqueue
),
1966 final_block_(final_blocker
, workqueue
)
1970 Task_block_token output_sections_block_
;
1971 Task_block_token final_block_
;
1975 Write_sections_task::locks(Workqueue
* workqueue
)
1977 return new Write_sections_locker(*this->output_sections_blocker_
,
1978 *this->final_blocker_
,
1982 // Run the task--write out the data.
1985 Write_sections_task::run(Workqueue
*)
1987 this->layout_
->write_output_sections(this->of_
);
1990 // Write_data_task methods.
1992 // We can always run this task.
1994 Task::Is_runnable_type
1995 Write_data_task::is_runnable(Workqueue
*)
2000 // We need to unlock FINAL_BLOCKER when finished.
2003 Write_data_task::locks(Workqueue
* workqueue
)
2005 return new Task_locker_block(*this->final_blocker_
, workqueue
);
2008 // Run the task--write out the data.
2011 Write_data_task::run(Workqueue
*)
2013 this->layout_
->write_data(this->symtab_
, this->of_
);
2016 // Write_symbols_task methods.
2018 // We can always run this task.
2020 Task::Is_runnable_type
2021 Write_symbols_task::is_runnable(Workqueue
*)
2026 // We need to unlock FINAL_BLOCKER when finished.
2029 Write_symbols_task::locks(Workqueue
* workqueue
)
2031 return new Task_locker_block(*this->final_blocker_
, workqueue
);
2034 // Run the task--write out the symbols.
2037 Write_symbols_task::run(Workqueue
*)
2039 this->symtab_
->write_globals(this->input_objects_
, this->sympool_
,
2040 this->dynpool_
, this->of_
);
2043 // Write_after_input_sections_task methods.
2045 // We can only run this task after the input sections have completed.
2047 Task::Is_runnable_type
2048 Write_after_input_sections_task::is_runnable(Workqueue
*)
2050 if (this->input_sections_blocker_
->is_blocked())
2055 // We need to unlock FINAL_BLOCKER when finished.
2058 Write_after_input_sections_task::locks(Workqueue
* workqueue
)
2060 return new Task_locker_block(*this->final_blocker_
, workqueue
);
2066 Write_after_input_sections_task::run(Workqueue
*)
2068 this->layout_
->write_sections_after_input_sections(this->of_
);
2071 // Close_task_runner methods.
2073 // Run the task--close the file.
2076 Close_task_runner::run(Workqueue
*)
2081 // Instantiate the templates we need. We could use the configure
2082 // script to restrict this to only the ones for implemented targets.
2084 #ifdef HAVE_TARGET_32_LITTLE
2087 Layout::layout
<32, false>(Sized_relobj
<32, false>* object
, unsigned int shndx
,
2089 const elfcpp::Shdr
<32, false>& shdr
,
2090 unsigned int, unsigned int, off_t
*);
2093 #ifdef HAVE_TARGET_32_BIG
2096 Layout::layout
<32, true>(Sized_relobj
<32, true>* object
, unsigned int shndx
,
2098 const elfcpp::Shdr
<32, true>& shdr
,
2099 unsigned int, unsigned int, off_t
*);
2102 #ifdef HAVE_TARGET_64_LITTLE
2105 Layout::layout
<64, false>(Sized_relobj
<64, false>* object
, unsigned int shndx
,
2107 const elfcpp::Shdr
<64, false>& shdr
,
2108 unsigned int, unsigned int, off_t
*);
2111 #ifdef HAVE_TARGET_64_BIG
2114 Layout::layout
<64, true>(Sized_relobj
<64, true>* object
, unsigned int shndx
,
2116 const elfcpp::Shdr
<64, true>& shdr
,
2117 unsigned int, unsigned int, off_t
*);
2120 #ifdef HAVE_TARGET_32_LITTLE
2123 Layout::layout_eh_frame
<32, false>(Sized_relobj
<32, false>* object
,
2124 const unsigned char* symbols
,
2126 const unsigned char* symbol_names
,
2127 off_t symbol_names_size
,
2129 const elfcpp::Shdr
<32, false>& shdr
,
2130 unsigned int reloc_shndx
,
2131 unsigned int reloc_type
,
2135 #ifdef HAVE_TARGET_32_BIG
2138 Layout::layout_eh_frame
<32, true>(Sized_relobj
<32, true>* object
,
2139 const unsigned char* symbols
,
2141 const unsigned char* symbol_names
,
2142 off_t symbol_names_size
,
2144 const elfcpp::Shdr
<32, true>& shdr
,
2145 unsigned int reloc_shndx
,
2146 unsigned int reloc_type
,
2150 #ifdef HAVE_TARGET_64_LITTLE
2153 Layout::layout_eh_frame
<64, false>(Sized_relobj
<64, false>* object
,
2154 const unsigned char* symbols
,
2156 const unsigned char* symbol_names
,
2157 off_t symbol_names_size
,
2159 const elfcpp::Shdr
<64, false>& shdr
,
2160 unsigned int reloc_shndx
,
2161 unsigned int reloc_type
,
2165 #ifdef HAVE_TARGET_64_BIG
2168 Layout::layout_eh_frame
<64, true>(Sized_relobj
<64, true>* object
,
2169 const unsigned char* symbols
,
2171 const unsigned char* symbol_names
,
2172 off_t symbol_names_size
,
2174 const elfcpp::Shdr
<64, true>& shdr
,
2175 unsigned int reloc_shndx
,
2176 unsigned int reloc_type
,
2180 } // End namespace gold.